Thermo switch



Feb. 26, 1957 Q JACKSON 2,783,329

THERMO SWITCH Filed Sept. 7, 1955 Fig. 1,0

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G/en Jackson INVENJOR.

United States Patent liice 2,783,329 Patented Feb. 26, 1957 THERM()SWITCH Glen Jackson, Indianapolis, Ind. Application September 7, 1955,Serial No. 532,831

3 Claims. (Cl..200 115.5)

This invention relates to thermo sensitive snap switches andparticularly to a plug-in circuit breaker of the manually reset typewhich is adapted to be used with any elec trical appliance.

An object of this invention is to provide an inexpensive thermoresponsive switch capable of being manually reset when the circuit withwhich it is connected becomes overloaded, thereby protecting the radio,television or other electrical equipment from being damaged in the eventthat a short circuit is developed.

Another object of this invention is to provide a circuit breaker of themanually reset type, which is capable of "being plugged directly intothe ordinary wall outlet and capable of accepting a customary prongedtype plug whereby it may be used by anyone capable of inserting anelectrical outlet plug into a receptacle.

These together with other objects and advantages which will become4subsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout, and in which:

'Figure l is a side view of the thermo responsive switch;

Figure 2 is a longitudinal sectional view taken substantially on theline 2 2 of Figure l;

Figure 3 is a longitudinal sectional View taken on the line 3 3 ofFigure 2;

Figure 4 is a longitudinal sectional view taken on the line 4 4 ofFigure 2; and

Figure 5 is a transverse sectional view taken on the line 5 5 of Figure2 and in the direction of the arrows.

The thermo responsive switch comprises a twopiece body having sections12 and 14 connected together by means of bolts 16 and 1S which passthrough aligned passages therein. The heads and nuts of these bolts arepreferably countersunk. lt is preferred that the body `section 12 and 14be made of electrically insulating material, such as Bakelite or someother plastic material.

*Prongs 20 and 22 protrude from one end of the body, one prong beingdiscontinuous and the other being continuous. Prong 22 is located in apassage 24 formed in the confronting surfaces of sections 12 and 14 andshaped to conform to the prong body or conductive strip 26. The prongproper 22 is formed by a returned portion of the prong body 26 and thereis an achoring leg 28 embedded in an angularly extending part of passage24. An offset 30 is formed in the prong body 26 adjacent the angulatedend 32 disposed in recess 34. Recess 34 is -actually an enlargement ofthe passage 24 near one end thereof, and the extreme end of the passage24 constitutes an appliance plug prong receiving slot 36. Angulated end32 of prong body 26 is suiciently springy to grip the appliance plugprong firmly so that good electrical continuity may be established.

The prong 20 is constructed similar to the prong 22 including theangular portion 38 which is similar in construction and function to theangular portion 28. However, the prong body strip terminates in an end40 which is disposed in a cavity 42. This cavity is formed in both bodysections 12 and 14 and has a bimetallic snap `spring 44 disposed in it.Also located in the cavity 42 is an end 46 of prong body 48, prong body48 being similar in shape -to the corresponding portion of prong body24. It includes an offset 50 together with an angulated end 52 that isdisposed in recess 54 formed in both of t-he body sections. Prongreceiving slot 56 which opens into recess 54 is adapted to accommodatean appliance plug prong and coacts with the slot 36 to accept the plug.

A partition 58 protruding from body section 12 extends across a reducedportion 60 of the cavity 42. This partition has a threaded bore 62 in itin order to accommod-ate the screw 64. Bimetallicfsnap spring 44 issecured -to the upper end of this screw whereby t-he location of snapspring 44 may be adjusted by rotation of screw 64. A reduced shank 68extends from screw 64 and is arranged parallel to the longitudinal axisthereof. This shank accommodates a push-button assembly 70 which extendsthrough an lopening formed in the confronting surfaces of the bodysections 12 and 14 and which communicates with cavity 42. Assembly 70 isof standard construction and includes a push button having a cavityaccommodating a return spring that is seated therein, the return springreacting on the push button and the reduced shank 68 yieldingly pressingthe push button outwardly of the section 12 of the body. In this way,the button assembly 70 may be pushed from the exterior of the body, andit has feet 71 4and 72 adapted to come to bear against spaced parts ofthe snap spring 44 in order to reset it.

This snap spring has contacts 74 and 76 at the ends thereof adapted torest on contacts 78 and 80 carried by the ends 40 and 46, respectively,of the interrupted prong 20.

In operation, the device 10 is inserted in an ordinary wall outlet or inany other outlet capable of accepting a plug. Then, the equipment plughas its prongs inserted in slots 36 and 56 and circuit continuity isestablished through the device 10. When there is a thermal overload, thebimetallic snap spring 44 will become distorted, thereby separatingthecontacts on it from the fixed contacts 78 and 80. This will open thecircuit with which the device 10 is associated. When it is desired toreset the switch and again close the circuit, the button assema Ibly 70is pushed, thereby pushing the feet 71 and 72 against the bimetallicsnap spring and, snapping it back to the position disclosed in Figure 2.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily -occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly, all suitable modifications and equivalentsmay be resorted to, falling within the scope of the invention asclaimed.

What is claimed as new is as follows:

l. A thermo sensitive switch adapted to be inserted in a receptacle andadapted to accommodate an electrical cord plug, said switch comprising abody having a rst body section and a second body section, meansextending through said sections fastening said sections together, aconductive strip carried by said body and embedded therein, saidconductive strip having a prong at one end thereof which protrudes fromthe end of said body, said body having a recess therein, the oppositeend of said strip having an angulated portion disposed in said recess,said body having a slot in communication with said recess at theopposite end of said body and adapted to accept one prong of anelectrical plug, an interrupted strip carried by said body, saidinterrupted strip including a prong protruding from the same end of saidbody as the previously mentioned prong, 4a strip portion having anangulated end, sa-id body having a slot in alignment with the recesswherein the last mentioned angulated portion is disposed, said lastmentioned slot adapted 'to accept a prong of a plug and coacting withthe previously mentioned slot to -accommodate an electrical equipmentplug, the last mentioned prong portion and strip portion having innerends spaced from each other, Va cavity in said body accommodating saidinner ends, a bimetallic snap spring having contacts at the ends thereofnormally touching said inner ends, -means `supporting said bimetallicsnap spring in said cavity and including a partition which extendsacross said cavity, a screw adjustably carried by said partition, saidsnap spring being disposed on said screw, and manually operable resetmeans for returning said bimetallic snap spring when it is distorted dueto a thermo overload condition.

2. The thermo sensitive switch of claim 1 wherein said manually operablereset means comprises a push button assembly carried by said body, saidassembly including a member which is movable inwardly of said cavity,and spaced means on said movable member adapted to contact said spacedvspring in order to deect said spaced spring.

3. The thermo lsensitive switch of claim 2 wherein said v spaced meanson said member comprise a pair of feet, and said feet being arranged tocontact said snap spring on opposite Isides of said screw.

References Cited in the le of this patent UNITED STATES PATENTS

